1. Field of the Invention
The present invention relates generally to a nail-pulling device having combined nail-pulling ends. More specifically, the present invention relates to a combination prying and nail-pulling device that provides a user with improved comfort, leverage, and overall ergonomic success, as well as to a method for employing the device to effect nail removal
2. Description of the Related Art
The related art involves the use of traditional tools to pry materials from surfaces such as nails affixed to flooring, walls, or roofing.
Using traditional tools, the nails are removed from such surfaces with a claw hammer or similar device. Optionally, a standard crowbar or other prying tool is used to pry the materials (such as adhered laminates from a counter top). The surfaces may be flat or curved, and may farther be angled. With respect to particularly difficult-to-remove items, and more particularly on difficult-to-access surfaces such as roofs or slanted walls, removal can be difficult since conventional prying tools tend to be generally straight or with very short (less than 90 degree) single-curve hooked pulling heads.
Such straight or hooked pulling heads do not provide sufficient leverage against the angled or awkwardly positioned surfaces, and pulling materials is difficult and slow, requiring repeated pulling to remove materials with a large surface area. Additionally, when dealing with particularly large materials (such as roofing tiles), the short curved surface is generally too short in length to provide an efficient detachment of the materials. Alternatively, when employing a conventional longer-slopped prying end positioned below such a roofing tile, the prying/lifting distance is detrimentally reduced by the construction geometry of the hooking member on an opposite end of the sloped prying end.
Conventional nail pulling and prying devices are recognized in the prior art. One common category of such devices are crowbar-type lever devices, which comprise a pulling head that is inserted under a particular material to be removed and a long shank, wherein prying-force is applied at the end of the shank opposite the head.
As can be seen in U.S. Pat. No. 6,629,684 (Youngren et al.) many crowbar type devices often employ a so-called “hooked” head, resulting in a single fulcrum (or single pivot point) relatively close to the head. In addition, the hooked head is relatively short, sometimes with an angle between the shaped portion of the hook and the shank at or near 90 degrees. This relatively limited curvature combined with the generally linear lever member projecting there from limits both the distance to which the hook can be inserted under the material to be pried, and the throw-distance through which a user may comfortably move the pry bar shank to achieve the pulling required. Additionally, this conventional construction also limits the position of a user's hands when initially locating the hook end under the item to-be-lifted (e.g. the head of a nail).
If the material is long or large, this shape requires the user to make repeated and incremental pulling-movements to remove long or large materials, particularly large sheeted materials such as roofing tiles, or where a nail is long (6 inches long or more) repeated pullings are required. Where the head is merely angled at approximately 90 degrees, the leverage to be applied is limited by the range of lever-motion the user can make before encountering the surface itself, i.e., the wall or roof, this phrase is used herein generally as referring to the user throw distance (the full range of lever-motion). In these cases, the nail pulling operation is inefficient since the upward motion of the material to be pulled is very limited by the shorter lever-motion range available, and may not exceed the length of the nail preventing removal. Lastly, many related art devices cause damage to the surface from which the materials are pulled where the pulling motion damages or creases the support surface. Some of these devices have two pry blades at opposite ends, with the opposing blade extending transversely to each other or in contrasting directions from each other.
Generally included in this category of pulling tools is the common claw-tooth hammer, which has a relatively short shank compared to a crowbar. These devices suffer from the drawback of having a short hook, but also from having a construction geometry prohibiting simple urging (driving) of the hook end under an item to be lifted. In such devices, the claw contains the relatively narrow fulcrum, and the curvature of the claw provides the leverage for a handle that projects at best 90 degrees from the pulling surface. While in the art of lever geometry it is known to increase leverage by employing a curve having a greater radius, what is not considered is the human ergonomic function in generating increased leverage when manipulating a very large radius lever. Thus, a solution to improving leverage (a large radius) is actually detrimental to operational use via decreased ergonomic function.
When using a conventional claw-tooth hammer device to remove nails, the claw must be inserted such that the nail shank is trapped between the two teeth of the claw and the nail head contacts the claw surface itself to enable simplified force transfer. As most nails have a very narrow shank, this means that most of the curvature of the claw used for pulling the nail is wasted, as the nail shank is generally trapped only when inserted deeply into the claw, leaving relatively little curvature left to rotate and provide leverage for extracting the nail.
Thus, using conventional art devices having a hooked curve or a very small or no curve, there is insufficient lift area and insufficient throw distance to effectively separate large surface-area materials or long nails from surfaces. In such cases, many small-pulling movements must be taken resetting the two teeth of the claw each time, rather than one or two large pulling actions that loosen much of the material in one movement. The user will appreciate that small pulling movements are inefficient and can cause undue stress on the body itself, particularly when the user is placing force against the lever arm at positions close to the pivot surfaces where interfering items may interfere with movement.
It would therefore be an advantage to have an improved combination nail pulling and prying device that provides both greater leverage and a greater range of movement than prior art devices when removing materials from surfaces, or when removing large or heavy materials. It would also be an advantage to have a combination device, which combines the functionality of a crowbar with an improved ergonomic function allowing a user greater range during force application to pull nails and other materials from surfaces.
As an example, reference is made now to FIGS. 1A, 1B, 1C, and 1D wherein a combination bar 1 is provided having a hook end 2 and a distal prying end 3 spaced by a bar shank member 10 having generally rounded corners 10′, 10″ for user comfort during gripping.
A nail slot 4 is positioned through bar shank member 10 proximate prying end 3 for use in removing nails retained therein. Opposing nail slots 5, 7 are respectively positioned centrally to pairs of sharp edges 6, 8 respectively as will be discussed.
Referring specifically now to FIG. 1B a common use position is depicted with combination bar 1 positioned projecting upwardly at approximately a 90 degree angle from a surface retaining a nail 9 having a nail shaft 16 (FIG. 1B). As can be seen, sharp edges 8, 8 on hook end 2 have been driven under the nail head of nail 9 by the application of a force F firmly seating the same within nail slot 7 for prying in a direction P, as shown. As can be seen, prying end 3 is projecting away from the direction of hook end 2 relative to a front side 14 and a rear side 15 of bar 1 respectively.
As is noted in the motion of seating, force F is applied to a first contact surface 12 offset a distance 13′ from a centerline of bar shank member 10 to force sharp edges 8, 8 about nail shaft 16, in a process generally referred to as seating. While not a suitable use, it is recognized that the opposing hand 200H of a user, positioned to providing force F may approach the support surface too closely and cause injury via slipping of contact surface 12. As a consequence, it is recognized as ergonomically awkward for the user to both position bar tool 1 via bar shank member 10 and provide seating force F while also guiding and positioning. Additionally, as a user's arms approach each to a distance generally less than a user's shoulder width this minimizes the ergonomic efficiency, control, and leverage involved and should be minimized. As a consequence, it is now recognized that a solution is needed that improves a user's ergonomic control and leverage while simultaneously allowing a user's arms to remain at a comfortable separation distance during use.
Referring specifically to FIG. 1C, bar tool 1 is shown positioned after a seating operation beneath head 9 of the nail about nail shaft 16 in a ready-to-lift position. As noted, hook end 2 is positioned on support surface 201, and the slightly curved outer surface of hook end 2 is shown in motion transiting to a contact position at the end of arc E, wherein pry end 3 contacts support surface 201 (distal end of bar 1 not shown).
A throw distance 120 (of approximately 6.5 cm (centimeters) in this example) is noted as the maximum support surface contact distance required by hook end 2 to reach the contact position from the ready-to-lift position. As will be discussed later, throw distance 120 is prohibitively long in an ergonomic and user-comfort sense, and requires a user to swing bar shank member 10 to at least an intermediate position along an arc D at a position 45 degrees off a vertical from support surface 201 to remove shaft 16 from support surface 120. It should be similarly appreciated that throw distance 120 requires movement fully to the contact position approximately 90 degrees off a vertical extending perpendicular from support surface 201 along an arc E to achieve a substantial removal of longer-shafted nails. This longer arc E is ergonomically detrimental because a user is capable of body leverage most comfortably along the shorter arch D (roughly a 45 degree transit on either side of a vertical position), thereby allowing a loss or minimization of leverage at a position between the two arcs (arc E-arc D).
Referring now specifically to FIG. 1D, an additional detriment of the conventionally related art bar shaft 1 is discussed. As shown, pry end 3 is positioned with sharp points 6 bounding shaft 16 thereby seating nail head 9 for an initial lift. This type of positioning is particularly suited for removing shingles or other sheet goods from angled surfaces but, as will be noted, is not an optimal operation in an ergonomic or user-comfort sense.
Due to the contrasting (or opposing) curve directions of pry end 3 and hook end 2 relative to front and back sides 14, 15 of bar 1, a maximum throw distance D1 is defined before sharp ends 8, 8, contact support surface 201. Should nail shaft 16 require additional pulling distance, bar 1 must be repositioned mid-shaft and a lift block included with the lifting/prying action begun again. Thus, those of skill in the art will recognize that it is beneficial to have a maximum throw distance D1 as great as possible for convenient nail removal and ergonomic efficiency.
Additionally, while positioning pry end 3 proximate nail shaft 16, a user may apply an urging force F2 in an attempt to fix sharp ends 6, 6 in a secure manner. Mechanical analysis suggests that the application of a force F2 is maximized when applied in manner best aligned with the length of bar shank member 10 which transmits force F2 to nail head 9. A detriment of the conventional design shown is that the only surface, surface 12′, sufficiently perpendicular to the length of bar shank member 10 to receive force F2 is positioned a distance 11 off (away from) a center line of bar shank member 10. Due to this off-center geometry, a number of detriments exist. First, the user providing force F2 along direction S urges surface 12′ thereby causing an elastic deflection 18 of hook 2 as force F2 is transmitted around hook 2 to bar shank member 10, and results consequently in a detriment and complementary elastic spring back action tending to dislodge shaft 16 from nail slot 5. Second, due to both the off center geometry and the resultant elastic spring back, the user (not shown) may attempt to present dislodgement by grasping bar shank member 10 proximate hook end 2, thereby placing a body portion in a position of absorbing the energy of said elastic spring back causing ergonomic discomfort and increased safety risk.
As a similar detriment a minor distance 13′ is defined between outer surface 12 and the centerline of bar shank member 10. During the prying motion noted in FIG. 1C, it shall be recognized that distance 13′ is detrimental to user comfort and security. In motion, the hand or hands 200H of user grasp pry end 3 of bar 1 and move the same along arc E until pry end 3 contacts support surface 201, at this point, due to the narrow range 13′ the hand or hands of a user either contact support surface 201 or may closely approach contact support surface 201 sufficient to prohibit the user from using maximum effort.
In a review of the above, those of skill in the art will recognize that what is not appreciated by the prior art is the need for a combination nail-pulling tool with increased user comfort and improved user ergonomics during prying activity on either end.
What is similarly not appreciated by the prior art is the need for a combination nail pulling tool with improved leverage during use and enhanced user throw while having both a pry end and a hook end projecting in a similar direction.
Accordingly, there is a need for an improved combination hand tool bar that responds to these detriments.